Psychoneuroendocrinology (2014) 49, 34—46 Available online at www.sciencedirect.com ScienceDirect jou rn al h om epage: www.elsevier.com/locate/psyneuen Impact of menstrual cycle phase on endocrine effects of partial sleep restriction in healthy women Amanda LeRoux a , Lisa Wright a , Tara Perrot a , Benjamin Rusak a,b,c,* a Department of Psychology & Neuroscience, Dalhousie University, Halifax, Nova Scotia, Canada b Department of Psychiatry, Dalhousie University, Halifax, Nova Scotia, Canada c Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia, Canada Received 24 January 2014; received in revised form 5 June 2014; accepted 5 June 2014 KEYWORDS Menstrual cycle; Hunger; Metabolism; Sleep; Mood; Cortisol; Circadian rhythm Summary There is extensive evidence that sleep restriction alters endocrine function in healthy young men, increasing afternoon cortisol levels and modifying levels of other hormones that regulate metabolism. Recent studies have confirmed these effects in young women, but have not investigated whether menstrual cycle phase influences these responses. The effects on cortisol levels of limiting sleep to 3 h for one night were assessed in two groups of women at different points in their menstrual cycles: mid-follicular and mid-luteal. Eighteen healthy, young women, not taking oral contraceptives (age: 21.8 ± 0.53; BMI: 22.5 ± 0.58 [mean ± SEM]), were studied. Baseline sleep durations, eating habits and menstrual cycles were monitored. Salivary samples were collected at six times of day (08:00, 08:30, 11:00, 14:00, 17:00, 20:00) during two consecutive days: first after a 10 h overnight sleep opportunity (Baseline) and then after a night with a 3 h sleep opportunity (Post-sleep restriction). All were awakened at the same time of day. Women in the follicular phase showed a significant decrease (p = 0.004) in their cortisol awakening responses (CAR) after sleep restriction and a sustained elevation in afternoon/evening cortisol levels (p = 0.008), as has been reported for men. Women in the luteal phase showed neither a depressed CAR, nor an increase in afternoon/evening cortisol levels. Secondary analyses examined the impact of sleep restriction on self-reported hunger and mood. Menstrual cycle phase dramatically altered the cortisol responses of healthy, young women to a single night of sleep restriction, implicating effects of spontaneous changes in endocrine status on adrenal responses to sleep loss. © 2014 Elsevier Ltd. All rights reserved. ∗ Corresponding author at: Department of Psychiatry, Dalhousie University, 8215 Lane Bldg., 5909 Veterans Memorial Lane, Halifax, Nova Scotia, Canada B3L 2E2. Tel.: +1 902 473 2433; fax: +1 902 473 4596. E-mail address: benjamin.rusak@dal.ca (B. Rusak). http://dx.doi.org/10.1016/j.psyneuen.2014.06.002 0306-4530/© 2014 Elsevier Ltd. All rights reserved.